142 rPvOGRESS OF MICROSCOPICAL SCIENCE. 



the embryo itself, is a very interesting fact for the partisans of the 

 doctrine of evolution, while it is inexplicable to those who believe in 

 the invariability of species." Among the phenomena of the third and 

 last evolution period, M. Balbiani mentions " the rupture of the serous 

 or external envelope of the cephalic region of the embryo, its concen- 

 tration on the dorsal surface as a crumpled mass, and, finally, its 

 penetration in the vitelline sac, or mid intestine, by an opening in the 

 back of the embryo. At the close of this period, a little horny plate 

 is found on the head of the larva, which enables it to split the mem- 

 brane at the time of hatching. M. Kiinckel has described and figured 

 this in P. fel'is, but M. Balbiani claims priority. 



The Circulation of the Blood in the Frog's Lung. — The following 

 mode of observing this phenomenon is thus described by Herr F. 

 Holmgren:* — The frog [Ecma esculenta is the jDreferable species) 

 is poisoned by several small doses of curare, so as to be paralyzed 

 for two or three days. A broad fold of the skin is taken up near 

 the armpit, and a curved needle, armed with a silk thread, is carried 

 thi'ough the basis of this fold, whereupon the thread is tied. In the 

 same manner a ligature is applied to the skin near the hind 

 legs. Between both ligatures a sufiicient portion of the skin and 

 the thin muscular layer is removed, when the inflated lung will 

 protrude through the wound, and soon collapse. The frog securely 

 fastened upon a board in the well-known manner, the lung is put into 

 a chamber which fits over the hole in the table of the microscope and 

 is closed at both ends by glass, to allow the light to pass from the 

 reflector through the chamber into the tube of the microscope. If now 

 the lung is inflated again through a rubber tube, a most beautiful view 

 of the circulation can be witnessed. 



Microscopic Examination of the Intestines in cases of Cholera. — A 

 valuable report which deals with the above subject has been recently 

 presented to the public by the U.S. Government. In this Dr. Dauforth, 

 who has had to do with the microscopical portion of the inquiry, says 

 that " under a power of about eighty diameters, the following appear- 

 ances are noted : the mucous and muscular layers seemed to have been 

 much disturbed in their relations, and separated widely apart ; between 

 them a very beautiful, loosely- woven web of areolar or connective tissue 

 is seen sending its delicate filaments across the intervening space, 

 with here and there a little vessel, making its way toward the mucous 

 layer ; the latter is unusually thin and unusually smooth on its free 

 sui'face ; not a single j)erfect villus can be seen, but a few ' stumps ' 

 of villi are easily made out, as though the missing portion had been 

 rudely torn away. Under a power of 260, the surfoce of the mucous 

 layer is seen to be almost, in fact quite denuded of epithelium, since 

 not a single normal club-shaped cell can be seen. The mucous 

 membrane seems to have passed through some scene of violence, during 

 which its villi have been wrenched from their attachments, and its 

 clothing of epithelium stripped from its surface and carried away. It 

 seems almost beyond belief that a few sliort liours could have so totally 

 * ' Cciilralhl. fur Cliir.,' No. 3'J. 



